Large commercial refrigerators with glass doors are commonly found in grocery stores and convenience stores where food and drinks are stored for access to customers.
FIGS. 1a and 1b (Prior Art) are, respectively a top plan, cutaway view and a perspective view of a conventional frame section. The frame section 10 includes an external member 12, an internal member 14 and a gasket 16 mounted to the external member 12 via a gasket support 18. An edge of a refrigerator door panel (not shown) on the cold side of the refrigerator sits on the gasket 16 when the door is closed. An insulating element 20 is inserted between the external and internal members 12, 14. Thermal bridges are formed by material of the external and internal members 12, 14, for example metal, that surround the insulating element 20.
FIG. 1c (Prior Art) is a cutaway view of a conventional rail surrounding the glass window of a refrigerator door. The glass window is, in the general case, a sealed glass unit (SGU) 24. A rail 25 is formed as a unitary piece that extends along a horizontal or vertical side of the refrigerator door. Usually, the horizontal vertical rails 25 are identically constructed, except for their overall lengths that are cut according to the horizontal and vertical dimensions of the SGU 24. A cover (not shown) can be mounted on a side 26 of the rail 25, snapping onto a hook 27 and a recess 28 on the side 26 of the rail. The SGU 24 is held in place between the cover and the right side 29 of the rail 25.
Refrigerator doors and frames must be sturdy in order to withstand frequent and sometimes careless opening and closing by customers. For that reason, refrigerator doors frames, horizontal door rails and vertical door rails (sometimes called ‘stiles’) are commonly made of steel or aluminum. Because these materials are good thermal conductors, condensation on refrigerator glass door panels is a significant problem. Use of other materials that are not good thermal conductors, for example polyvinyl chloride (PVC), is generally not practical because they these materials will break even when subject to modest abuse.
Shop owners desire to keep their glass doors free of any fogging in order to allow customers to clearly see the products that are available on refrigerator shelves. A common solution to the condensation problem is to install cable heating elements 21 within an open space 22 defined in refrigerator door frames and cable heating elements 23 onto the side 26 of the rail 25, the cable heating elements 23 being protected by the cover mounted on the side 26 of the rail 25. While this solution is effective in preventing condensation, it is highly inefficient in terms of energy consumption. Given the opposite requirements of keeping the inside of the refrigerator cold while keeping the door frames warm, electrical energy waste is considerable.
Therefore, there is a need for improvements in the construction of refrigerator doors and door frames that compensate for problems related to condensation and to waste of energy.